Chemical treatment for lithography improvement in a negative tone development process

ABSTRACT

A material layer is formed over a substrate. A negative tone photoresist layer is formed over the material layer. An exposure process is performed to the negative tone photoresist layer. A post-exposure bake (PEB) process is performed to the negative tone photoresist layer. After the exposure process and the PEB process, the negative tone photoresist layer is treated with a solvent. The solvent contains a chemical having a greater dipole moment than n-butyl acetate (n-BA).

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. However, these advances haveincreased the complexity of processing and manufacturing ICs and, forthese advances to be realized, similar developments in IC processing andmanufacturing are needed. In the course of integrated circuit evolution,functional density (i.e., the number of interconnected devices per chiparea) has generally increased while geometry size (i.e., the smallestcomponent (or line) that can be created using a fabrication process) hasdecreased.

As the semiconductor device sizes continue to shrink, for example below20 nanometer (nm) nodes, negative tone development (NTD) processes maybe needed to achieve the small device sizes. However, even NTD processesmay still have drawbacks related to depth of focus (DOF), line widthroughness (LWR), or scum. These issues degrade lithography performanceand may lead to decreased yield or even device failures.

Therefore, while existing NTD processes have been generally adequate fortheir intended purposes, they have not been entirely satisfactory inevery aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIGS. 1-4 are diagrammatic cross-sectional side views of a semiconductordevice at various stages of fabrication in accordance with someembodiments of the present disclosure.

FIG. 5 is a flowchart illustrating a method of fabricating asemiconductor device in accordance with some embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As the semiconductor industry keeps shrinking device sizes (e.g., below20 nanometer nodes), traditional positive tone development (PTD)processes face challenges related to optical restriction, which may leadto poor resolution. Therefore, negative tone development (NTD) processeshave been used to pattern certain semiconductor elements such as contactholes or trenches. For NTD processes, a sufficiently good optical imagemay be achieved with bright filed mask application. However, althoughthe lithography performance of NTD processes is typically better thanPTD processes, NTD processes may still have certain shortcomings. Forexample, NTD processes may suffer from narrow depth of focus (DOF)problems due to unsatisfactory footing and tapper profile. As anotherexample, NTD processes may result in poor line width roughness (LWR) dueto large grain sizes. As yet another example, NTD processes may alsocause too much scum to be generated, which is due to photoresist areaswith poor optical contrast being too sensitive to increased acidity fromthe mask layer therebelow (e.g., Si-HM).

To overcome these issues associated with NTD processes discussed above,the present disclosure provides a novel chemical treatment ofphotoresist as a part of an improved NTD process. The various aspects ofthe present disclosure will be discussed below in greater detail withreference to FIGS. 1-5.

FIGS. 1-4 are diagrammatic fragmentary cross-sectional side views of asemiconductor device 35 at various stages of fabrication in accordancewith various aspects of the present disclosure. The semiconductor device35 may include an integrated circuit (IC) chip, system on chip (SoC), orportion thereof, and may include various passive and activemicroelectronic devices such as resistors, capacitors, inductors,diodes, metal-oxide semiconductor field effect transistors (MOSFET),complementary metal-oxide semiconductor (CMOS) transistors, bipolarjunction transistors (BJT), laterally diffused MOS (LDMOS) transistors,high power MOS transistors, or other types of transistors.

Referring to FIG. 1, a semiconductor device 35 includes a substrate 40.In some embodiments, the substrate 40 is a silicon substrate doped witha p-type dopant such as boron (for example a p-type substrate).Alternatively, the substrate 40 could be another suitable semiconductormaterial. For example, the substrate 40 may be a silicon substrate thatis doped with an n-type dopant such as phosphorous or arsenic (an n-typesubstrate). The substrate 40 could include other elementarysemiconductors such as germanium and diamond. The substrate 40 couldoptionally include a compound semiconductor and/or an alloysemiconductor. Further, the substrate 40 could include an epitaxiallayer (epi layer), may be strained for performance enhancement, and mayinclude a silicon-on-insulator (SOI) structure.

In some embodiments, the substrate 40 is substantially conductive orsemi-conductive. The electrical resistance may be less than about 10³ohm-meter. In some embodiments, the substrate 40 contains metal, metalalloy, or metal nitride/sulfide/selenide/oxide/silicide with the formulaMXa, where M is a metal, and X is N, S, Se, O, Si, and where “a” is in arange from about 0.4 to 2.5. For example, the substrate 40 may containTi, Al, Co, Ru, TiN, WN2, or TaN.

In some other embodiments, the substrate 40 contains a dielectricmaterial with a dielectric constant in a range from about 1 to about 40.In some other embodiments, the substrate 40 contains Si, metal oxide, ormetal nitride, where the formula is MXb, wherein M is a metal or Si, andX is N or O, and wherein “b” is in a range from about 0.4 to 2.5. Forexample, the substrate 40 may contain SiO₂, silicon nitride, aluminumoxide, hafnium oxide, or lanthanum oxide.

A material layer 50 is formed over the substrate 40. The material layer50 can be patterned via a lithography process and as such may also bereferred to as a patternable layer. It is understood that the materiallayer 50 may serve as a hard mask, which can be used to pattern layersunderneath after its own pattern has been defined by a patternedphotoresist (to be formed thereabove). Thus, the material layer 50 maybe referred to as a Si hard mask (Si-HM). In an embodiment, the materiallayer 50 includes a dielectric material, such as silicon oxide orsilicon nitride. In another embodiment, the material layer 50 includesmetal. In yet another embodiment, the material layer 50 includes asemiconductor material.

In some embodiments, the material layer 50 has different opticalproperties than photoresist. For example, the material layer 50 has adifferent n, k, or T value from photoresist. In some embodiments, thematerial layer 50 comprises at least one of different polymer structure,acid labile molecule, PAG (photo acid generator) loading, quencherloading, chromophore, cross linker, or solvent, which lead to differentn value to photoresist. In some embodiments, the material layer 50 andphotoresist have different etching resistance. In some embodiments, thematerial layer 50 contains an etching resistant molecule. The moleculeincludes low onishi number structure, double bond, triple bond, silicon,silicon nitride, Ti, TiN, Al, aluminum oxide, SiON, or combinationsthereof.

It is understood that the substrate 40 and the material layer 50 mayeach include additional suitable material compositions in otherembodiments. It is also understood that additional layers may be formedbetween the substrate 40 and the material layer 50, but they are notillustrated herein for reasons of simplicity.

A photoresist layer 60 is formed over the material layer 50. Thephotoresist layer 60 includes a negative tone photoresist (also referredto as negative photoresist). Compared to a positive tone photoresist,where the portion of the photoresist exposed to light becomes soluble toa developer solution, the portions of the negative tone photoresistexposed to light remains insoluble to the developer solution. In someembodiments, the photoresist layer 60 may be formed by a spin-coatingprocess. The photoresist layer 60 may contain components such as apolymer, photo acid generators (PAG), solvent, quenchers, chromophore,surfactant, cross linker, etc.

An exposure process is performed to expose desired portions of thephotoresist layer 60. As a part of the exposure process, a photomask 70(or a reticle) is positioned above the photoresist layer 60. As anillumination source, radiation such as ultraviolet (UV) light 80 isprojected toward the photomask 70 from above. In some embodiments, theUV light has an illumination wavelength substantially less than 250 nmand comprises at least one of: KrF, ArF, EUV, or E-beam.

The photomask 70 has opaque portions 90, which will block radiation suchas the UV light 80. Between the opaque portions 90 are transparentregions 100, which allow the UV light 80 to propagate through toward thephotoresist layer 60 and expose the portions 60A of the photoresistlayer 60 underneath. As a result of the UV light exposure, the portions60A become crosslinked/polymerized and more difficult to dissolve in adeveloper solution.

Referring now to FIG. 2, a post exposure bake process 110 is performedto the semiconductor device 35 after the exposure process. In someembodiments, the post exposure bake process 110 may be performed at atemperature range between about 100 degrees Celsius and about 120degrees Celsius for several minutes. The post exposure bake process 110catalytically performs and completes the photo reaction initiated insidethe photoresist layer 60 during the exposure process. The post exposurebake process 110 also helps remove solvent from the photoresist layer60. As a result, the adhesion and etching resistance of the photoresistlayer 60 are improved.

Referring now to FIG. 3, a developing process 120 is performed todevelop the photoresist layer 60. A developer solution is applied to thephotoresist layer 60 as a part of the developing process 120. In someembodiments, the developer solution includes n-butyl acetate (n-BA). Asis shown in FIG. 3, the developer solution washes away the portions ofthe photoresist layer 60 that are not exposed to the UV light 80, butthe portions 60A of the photoresist layer 60 exposed to the UV light 80still remains.

However, photoresist scum 130 (also referred to as photoresist residueor blind) may still remain at the bottom of the photoresist portions60A. The presence of the photoresist scum 130 may be due to theincreased acidity of the material layer 50 (i.e., the Si-HM). In moredetail, in an NTD process, the acidity of the material layer 50 isincreased to improve the undercut profile issue (undercut profile issuecaused by inadequate polarity change of photoresist bottom area).Unfortunately, some photoresist areas with poor optical contrast are toosensitive to acid from the material layer 50. These areas may thengenerate the photoresist scum 130 shown in FIG. 3. If not removed, thephotoresist scum 130 may adversely affect the patterning accuracy of thematerial layer 50. In other words, the material layer 50 may not be ableto achieve its desired pattern shape due to the presence of thephotoresist scum 130.

To facilitate the removal of the photoresist scum 130, the presentdisclosure applies a chemical treatment process 140 to the photoresistscum 130, as shown in FIG. 4. A solvent (or chemical) is used to rinsethe photoresist scum 130 as a part of the chemical treatment process140. The solvent has high polarity. In some embodiments, the solvent hasa dipole moment higher than n-BA, for example the dipole moment of thesolvent may be greater than about 1.9 D. The solvent is a chemicalinteraction force that is capable of removing the photoresist scum 130and/or curing the other issues of NTD process discussed above, such asDOF enlargement, diminished end-to-end distance, or line width roughness(LWR).

It is understood that the solvent may be a pure solvent or a co-solventwith n-BA. In embodiments where the solvent is a co-solvent with n-BA,the n-BA ratio in the combined solvent is greater than about 10%,otherwise the photoresist portions 60A may be at least partiallydissolved, which is undesirable as that would also adversely impact thesubsequent patterning of the material layer 50. It is also understoodthat if the solvent is a co-solvent with n-BA, they may be mixedtogether at a photoresist coating tool (e.g., track). In other words,the chemical material of the solvent need not necessarily be premixedwith the n-BA. Instead, the chemical material of the solvent may bemixed with the n-BA using a standard coating tool for applying thedeveloper solution during the actual fabrication of the semiconductordevice 35. The mixing ratio of the solvent and the n-BA may becontrolled by the coating tool, or with the coating recipe. In thismanner, the present disclosure does not require complicated additionalfabrication steps, since existing fabrication equipment (e.g., thecoating tool/track herein) may be easily leveraged.

According to the various aspects of the present disclosure, there areseveral designs for the solvent. In a first design, the solvent containschemical A. In some embodiments, the chemical A is propylene glycolmonomethyl ether (PGME). In other embodiments, the chemical A is OK73,which is about 70% PGME and about 30% propylene glycol methyl etheracetate (PGMEA). In other words, the PGME/PGMEA has a 70/30concentration percentage in OK73. The chemical A can dissolve (andthereby remove) the photoresist scum 130.

In a second design, the solvent contains chemical B, which includeschemical A discussed above with an additive added thereto. Stateddifferently, the chemical B is a blend of chemical A and the additive.In more detail, although the chemical A discussed above can dissolve thephotoresist scum 130 well, the high polarity of the chemical A may causephotoresist film thickness loss, which is undesirable. To ease thisconcern, the additive is added herein as a part of chemical B in orderto decrease photoresist film loss and increase contrast.

In some embodiments, the additive includes amine derivatives NR1R2R3,wherein R1, R2, R3 may be the same or different materials. R1, R2, andR3 may each represent a hydrogen atom, an alkyl group (e.g., an alkylgroup having a carbon number of 1 to 20), a cycloalkyl group (e.g., acycloalkyl group having a carbon number of 3 to 20), or an aryl group(e.g., an aryl group having a carbon number of 6 to 20). In someembodiments, R2 and R3 may combine with each other to form a ring. Insome embodiments, the alkyl group having a substituent may be anaminoalkyl group having a carbon number of 1 to 20, a hydroxylalkylgroup having a carbon number of 1 to 20, or cyanoalkyl group having acarbon number of 1 to 20. In some embodiments, the structure for theadditive includes guanidine, aminopyrrolidine, pyrazole, pyazoline,piperazine, aminomorpholine, aminialkylmorpholine, or piperidine. Insome embodiments, the additive in chemical B can also be photo-sensitiveor thermal-sensitive to change its PH value.

In a third design, the solvent contains chemical C. Similar to chemicalB, the chemical C includes an additive that is blended to chemical A toease the photoresist film thickness loss concerns. Unlike chemical B,however, the chemical C does not contain the amine derivatives NR1R2R3but rather contains triphenylsulfonium (TPS) salt derivatives. In someembodiments, the additive in chemical C can also be photo-sensitive orthermal-sensitive to change its PH value.

It is understood that the second design (chemical B) or the third design(chemical C) are optional, and that they may not be needed if the firstdesign (chemical A) is capable of removing the photoresist scum 130without degrading the desired photoresist pattern formed by thephotoresist portions 60A. Regardless of which design is used for thesolvent, the end result is that the photoresist scum 130 is removed bythe chemical treatment process 140, while the desired photoresistportions 60A still remain.

It is understood that some standard lithography processes may beperformed but are not specifically discussed herein for reasons ofclarity and simplicity. For example, a hard bake process may beperformed after the developing process 120 but before the chemicaltreatment process 140. In addition, the process flow discussed abovewith reference to FIGS. 1-4 shows the chemical treatment process 140being performed after the “standard” developing process 120 using n-BAas a developer. However, it is understood that the order in which theprocesses 120 and 140 are performed is not critical. In some alternativeembodiments, the chemical treatment process 140 may be performed beforethe developing process 120. It some other alternative embodiments, theprocesses 120 and 140 may also be performed together or simultaneously.In other words, the solvent (using either chemical A, chemical B, orchemical C) and the n-BA developer may be applied to the photoresistlayer 60 at the same time.

After the developing process 120 and the chemical treatment process 140are performed, subsequent patterning processes may be performed usingthe patterned photoresist as a mask. For example, the material layer 50(e.g., Si-HM) may be patterned into a mask layer to further pattern thelayers therebelow. The patterned photoresist may be removed by aphotoresist removal process known in the art, such as a stripping or anashing process.

FIG. 5 is a flowchart of a method 200 of forming a semiconductor patternaccording to various aspects of the present disclosure. The method 200may be performed as a part of a lithography process.

The method 200 includes a step 210 of forming a patternable layer over asubstrate. In some embodiments, the substrate is substantiallyconductive or semi-conductive. In some embodiments, the substratecontains metal, metal alloy, or metalnitride/sulfide/selenide/oxide/silicide with the formula MXa, where M isa metal, and X is N, S, Se, O, Si, and where “a” is in a range fromabout 0.4 to 2.5. For example, the substrate 40 may contain Ti, Al, Co,Ru, TiN, WN2, or TaN. In some other embodiments, the substrate containsa dielectric material with a dielectric constant in a range from about 1to about 40. In some other embodiments, the substrate contains Si, metaloxide, or metal nitride, where the formula is MXb, wherein M is a metalor Si, and X is N or O, and wherein “b” is in a range from about 0.4 to2.5. For example, the substrate may contain SiO2, silicon nitride,aluminum oxide, hafnium oxide, or lanthanum oxide.

The patternable layer formed over the substrate has different opticalproperties than photoresist. For example, the layer has a different n,k, or T value from photoresist. In some embodiments, the layer comprisesat least one of different polymer structure, acid labile molecule, PAG(photo acid generator) loading, quencher loading, chromophore, crosslinker, or solvent, which lead to different n value to photoresist. Insome embodiments, the layer and photoresist have different etchingresistance. In some embodiments, the layer contains an etching resistantmolecule. The molecule includes low onishi number structure, doublebond, triple bond, silicon, silicon nitride, Ti, TiN, Al, aluminumoxide, SiON, or combinations thereof. It is understood that additionallayers may be formed between the patternable layer and the substrate.

The method 200 includes a step 220 of coating a negative tonephotoresist layer over the layer.

The method 200 includes a step 230 of performing an exposure process tothe negative tone photoresist layer.

The method 200 includes a step 240 of performing a post-exposure bake(PEB) process to the negative tone photoresist layer.

The method 200 includes a step 250 of performing a negative tonedeveloping process to the negative tone photoresist layer. The negativetone developing process is performed using n-butyl acetate (n-BA) as adeveloper in some embodiments.

The method 200 includes a step 260 of performing a chemical treatmentprocess to the negative tone photoresist. The chemical treatment processincludes applying a chemical having a greater dipole moment than about1.9 D. The chemical contains propylene glycol monomethyl ether acetate(PGMEA) or a combination of propylene glycol monomethyl ether (PGME) andPGMEA (e.g., OK73).

In some embodiment, the chemical of step 260 is applied as a part of asolvent, where the solvent may also include n-BA. A ratio of the n-BA inthe solvent is greater than about 10%.

In some embodiments, the chemical of step 260 further contains anadditive. The additive may include amine derivatives NR1R2R3. R1, R2,and R3 may each represent a hydrogen atom, an alkyl group (e.g., analkyl group having a carbon number of 1 to 20), a cycloalkyl group(e.g., a cycloalkyl group having a carbon number of 3 to 20), or an arylgroup (e.g., an aryl group having a carbon number of 6 to 20). In someembodiments, R2 and R3 may combine with each other to form a ring. Insome embodiments, the alkyl group having a substituent may be anaminoalkyl group having a carbon number of 1 to 20, a hydroxylalkylgroup having a carbon number of 1 to 20, or cyanoalkyl group having acarbon number of 1 to 20. In some embodiments, the structure for theadditive includes guanidine, aminopyrrolidine, pyrazole, pyazoline,piperazine, aminomorpholine, aminialkylmorpholine, or piperidine.

In some other embodiments, the additive may also includetriphenylsulfonium (TPS) salt derivatives.

In some embodiments, the additive is photo-sensitive orthermal-sensitive to change its PH value.

It is understood that the steps 250 and 260 need not be performedsequentially. In some embodiments, the negative tone developing processin step 250 is performed before the chemical treatment process in step260. In some other embodiments, the negative tone developing process instep 250 is performed after the chemical treatment process in step 260.In yet other embodiments, the negative tone developing process in step250 and the chemical treatment process in step 260 may be performedtogether or simultaneously.

It is also understood that additional processes may be performed before,during, or after the steps 210-260 of the method 200 to complete thefabrication of the semiconductor device. For example, the method 200 mayinclude additional processes to pattern the patternable layer, and usingthe patternable layer as a mask to pattern layers therebelow. As anotherexample, the exposure process discussed herein may be done using aradiation having a first wavelength, and the photoresist may later beexposed by a radiation having a second wavelength (e.g., as a part of adouble patterning process). For reasons of simplicity, these additionalsteps are not discussed herein in detail.

Based on the above discussions, it can be seen that the presentdisclosure offers advantages over conventional methods. It isunderstood, however, that other embodiments may offer additionaladvantages, and not all advantages are necessarily disclosed herein, andthat no particular advantage is required for all embodiments. Oneadvantage is that the chemical treatment process discussed above cansufficiently and effectively remove photoresist scum that is generatedas a part of a NTD process. As a result, the photoresist pattern has amore clearly and precisely defined profile, and issues plaguing NTDprocesses such as narrow DOF, poor LWR, etc., may disappear. This allowsthe NTD lithography to achieve smaller device sizes. Another advantageis that the solvent used in the chemical treatment may be applied viaexisting coating tools. Therefore, the processes of the presentdisclosure are compatible with existing process flow and do notsignificantly increase fabrication costs or time.

One embodiment of the present disclosure pertains to a method offabricating a semiconductor device. A material layer is formed over asubstrate. A negative tone photoresist layer is coated over the materiallayer. An exposure process is performed to the negative tone photoresistlayer. A post-exposure bake (PEB) process is performed to the negativetone photoresist layer. After the exposure process and the PEB process,the negative tone photoresist layer is treated with a solvent. Thesolvent contains a chemical having a greater dipole moment than n-butylacetate (n-BA).

Another embodiment of the present disclosure pertains to a method offabricating a semiconductor device. A patternable layer is formed over asubstrate. A negative tone photoresist layer is formed over thepatternable layer. An exposure process is performed to the negative tonephotoresist layer. A post-exposure bake (PEB) process is performed tothe negative tone photoresist layer. A negative tone developing processis performed to the negative tone photoresist layer. The negative tonedeveloping process is performed using n-butyl acetate (n-BA) as adeveloper. A chemical treatment process is performed to the negativetone photoresist. The chemical treatment process includes applying achemical having a greater dipole moment than about 1.9 D. The chemicalcontains propylene glycol monomethyl ether acetate (PGMEA) or acombination of propylene glycol monomethyl ether (PGME) and PGMEA. Thechemical treatment process may be performed before, during, or after thenegative tone developing process.

Yet another embodiment of the present disclosure pertains to a method offabricating a semiconductor device. A material layer is formed over asubstrate. A negative tone photoresist layer is coated over the materiallayer. An exposure process is performed to the negative tone photoresistlayer. A post-exposure bake (PEB) process is performed to the negativetone photoresist layer. A negative tone developing process is performedto the negative tone photoresist layer. The negative tone developingprocess is performed using n-butyl acetate (n-BA) as a developer. Thenegative tone photoresist layer is treated with a solvent. The solventcontains a chemical and an additive. The chemical contains propyleneglycol monomethyl ether acetate (PGMEA) or a mix of propylene glycolmonomethyl ether (PGME) and PGMEA with about a 70/30 concentrationpercentage. The additive contains amine derivatives ortriphenylsulfonium (TPS) salt derivatives.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method of fabricating a semiconductor device,comprising: forming a material layer over a substrate, wherein thematerial layer has an acidity; coating a negative tone photoresist layerover the material layer; performing an exposure process to the negativetone photoresist layer; performing a post-exposure bake (PEB) process tothe negative tone photoresist layer; developing the negative tonephotoresist layer after the PEB process, wherein photoresist scumremains at a bottom of a developed negative tone photoresist layer,wherein the photoresist scum is produced due to a sensitivity of thenegative tone photoresist layer to the acidity of the material layer;and removing the photoresist scum from the developed negative tonephotoresist layer using a solvent, wherein the solvent contains achemical having a greater dipole moment than n-butyl acetate (n-BA). 2.The method of claim 1, wherein the chemical contains at least one of:propylene glycol monomethyl ether (PGME) and propylene glycol monomethylether acetate (PGMEA).
 3. The method of claim 1, wherein the solventfurther contains n-BA, wherein a ratio of the n-BA in the solvent isgreater than about 10%.
 4. The method of claim 1, wherein the solventfurther contains an additive.
 5. The method of claim 4, wherein theadditive includes amine derivatives NR1R2R3, wherein R1, R2, and R3 mayeach represent a hydrogen atom, an alkyl group, a cycloalkyl group, oran aryl group.
 6. The method of claim 5, wherein R2 and R3 combine witheach other to form a ring.
 7. The method of claim 4, wherein theadditive includes triphenylsulfonium (TPS) salt derivatives.
 8. Themethod of claim 4, wherein the additive is photo-sensitive orthermal-sensitive.
 9. The method of claim 1, further comprising:performing a negative tone development process to the negative tonephotoresist layer.
 10. The method of claim 9, wherein the negative tonedevelopment process is performed using n-BA as a developer.
 11. Themethod of claim 9, wherein the negative tone development process isperformed before the removing of the photoresist scum.
 12. The method ofclaim 9, wherein the negative tone development process is performedafter the removing of the photoresist scum.
 13. The method of claim 9,wherein the negative tone development process and the removing of thephotoresist scum are performed simultaneously.
 14. A method offabricating a semiconductor device, comprising: forming a patternablelayer over a substrate, the patternable layer being a non-photosensitivelayer and has an acidity; forming a negative tone photoresist layer overthe patternable layer; performing an exposure process to the negativetone photoresist layer; performing a post-exposure bake (PEB) process tothe negative tone photoresist layer; performing a negative tonedeveloping process to the negative tone photoresist layer, wherein thenegative tone developing process is performed using n-butyl acetate(n-BA) as a developer, and wherein a photoresist scum is produced due toa sensitivity of the negative tone photoresist layer to the acidity ofthe patternable layer, and wherein the photoresist scum remains at abottom of a developed negative tone photoresist layer after the negativetone developing process has been performed; and performing a chemicaltreatment process to the developed negative tone photoresist layer toremove the photoresist scum by applying a chemical having a greaterdipole moment than about 1.9D, wherein the chemical contains propyleneglycol monoinethyl ether acetate (PGMEA) or a combination of propyleneglycol monomethyl ether (PGME) and PGMEA, and wherein the chemicaltreatment process is performed after the negative tone developingprocess.
 15. The method of claim 14, wherein the chemical furthercontains amine derivatives or triphenylsulfonium (TPS) salt derivatives.16. The method of claim 15, wherein the amine derivatives includeNR1R2R3, wherein R1, R2, and R3 may each represent a hydrogen atom, analkyl group, a cycloalkyl group, or an aryl group.
 17. The method ofclaim 16, wherein R2 and R3 combine with each other to form a ring. 18.The method of claim 15, wherein the chemical is photo-sensitive orthermal-sensitive.
 19. A method of fabricating a semiconductor device,comprising: forming a dielectric material layer over a substrate, thedielectric material layer being non-photosensitive and contains an acid;coating a negative tone photoresist layer over the dielectric materiallayer; performing an exposure process to the negative tone photoresistlayer; performing a post-exposure bake (PEB) process to the negativetone photoresist layer; performing a negative tone developing process tothe negative tone photoresist layer, wherein the negative tonedeveloping process is performed using n-butyl acetate (n-BA) as adeveloper, and wherein the negative tone developing process leavesphotoresist scum at a bottom of a developed negative tone photoresistlayer as a result of a reaction between the dielectric material layerand portions of the photoresist layer that are sensitive to the acid ofthe dielectric material layer; and removing the photoresist scum bytreating the developed negative tone photoresist layer with a solvent,wherein the solvent contains a chemical and an additive; wherein: thechemical contains propylene glycol inonomethyl ether acetate (PGMEA) ora mix of propylene glycol monomethyl ether (PGME) and PGMEA with about a70/30 concentration percentage, and the additive contains aminederivatives or triphenylsulfonium (TPS) salt derivatives.
 20. The methodof claim 19, wherein amine derivatives include NR1R2R3, wherein R1, R2,and R3 may each represent a hydrogen atom, an alkyl group, a cycloalkylgroup, or an aryl group.